It kinda depends on what room type you are playing. I am pretty sure that when you are playing a moltke in Blitz without R slots that it is kinda useless...
All KM BBs have great AA spots. I advise you to load the level 30 AA guns on your BB1-4s and the level 42? on the 5-6s. The point of having AA on your BB is give cover to yourself and your closeby teammates.
It used to be handy to blind the enemy with it, but wouldn't trust to much on it with all the bugs/desyncs and subs. Had it very often that I killed all scouts in my surrounding, knowing that there is no sub near me, and that I somehow catch three full hits from the enemy *_*
I still use my AA to kill all kinds of planes nearby, but I am not going to use its "advantage" anymore. A last tip is to keep in mind that you are battleship and you ll be fine.